The longterm goal of the proposed research is to determine the contribution of oxidative DNA damage-associated mutation to aging and to the pathogenesis of age-associated disease. The specific aims of the proposed research focus on the molecular markers of oxidative DNA damage and mutation in human, mouse and avian tissues that have different intrinsic antioxidant defense capacities, or in which antioxidant defense capacity has been experimentally modified. We will determine levels of 2 oxidative DNA damage adducts (5-OH-dC and 8-oxo-dG) and the frequency of oxidative damage-associated CC to TT mutations and of randomly distributed mutations in mtDNA from human, mouse and avian cells. We will also determine the frequency and molecular spectrum of HPRT mutations in human and mouse kidney. The explicit hypothesis we will test is that enhanced antioxidant defense capacity will be associated with lower levels of both oxidative DNA damage and mutation in vivo. Results of this work will allow us to determine the relationship of mtDNA damage and mutation to organellar dysfunction, and the spectrum of nuclear DNA mutations as a function of age, species and antioxidant defense capacity.